Yo-yos most commonly are made from wood or from a molded plastic as the principal material of construction. Yo-yos made from different materials present a different feel to the yo-yo player, some players preferring the feel of one over the other. Some yo-yos have been made from metal which presents still another feel that may be preferred by some players. Few metal yo-yos have been commercialized, however, and, as to those, their availability has been limited possibly because the typical construction for such yo-yos is costly and is substantially more than that of a more conventional yo-yo made from plastic or wood. In one prior art construction, the metal yo-yo may be formed from aluminum by machining the yo-yo halves that will be assembled to form the yo-yo body in a milling machine from solid round aluminum bar stock. The entire yo-yo half is formed, in one piece, from the round aluminum bar stock. The end of the bar stock is milled to form the outer face of the yo-yo half by removing an annular region of material, leaving a center hub and a peripheral rim. The peripheral contour of the yo-yo half also may be milled, as may be the inner face of the yo-yo half. The milled piece then is cut-off from the round bar stock to a thickness appropriate for the yo-yo half. The inner face of the yo-yo half then is machined further by drilling and tapping a center hole along the central axis of the yo-yo half to accept the threaded end of an axle by which two yo-yo halves will be joined. After machining, the yo-yo halves then are individually polished and finished. Such one-piece yo-yo halves are made individually in a labor intensive process that is wasteful of material, all of which adds to the cost of the yo-yo.
Also among the desirable features of a yo-yo, especially for those users who wish to perform complex string tricks, is to provide a wide peripheral entry to the string slot between the yo-yo halves. Yo-yos having such a wide entry sometimes are referred to as having a "butterfly" configuration. While incorporating a butterfly configuration in a plastic injection molded yo-yo is simply a matter of configuring the mold for the yo-yo halves, the fabrication of a butterfly yo-yo from metal, using the prior art milling technique described above, presents additional difficulties in milling the peripheral surfaces as well as the inner surfaces of the yo-yo halves. Such milling results in still further waste of material and additional labor and other expenses attendant to finishing the surfaces of the yo-yo halves. The milled one-piece metal yo-yo involves a machining process that can be expected to leave marks and other irregular surface regions that should be finished to a smoother surface in order to accept a desired finish, such as anodizing or finishing graphics. The milled metal yo-yo halves do not lend themselves to mass finishing but, instead, must be finished individually, adding further to the cost of the yo-yo.
It would be desirable to provide a metal yo-yo embodying a construction and method of manufacture that would reduce substantially the cost and ease of manufacture while providing a metal yo-yo with desirable characteristics, including the ability to form a butterfly yo-yo.